The CAS Registry Mumber 98791-12-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,8,7,9 and 1 respectively; the second part has 2 digits, 1 and 2 respectively. Calculate Digit Verification of CAS Registry Number 98791-12: (7*9)+(6*8)+(5*7)+(4*9)+(3*1)+(2*1)+(1*2)=189 189 % 10 = 9 So 98791-12-9 is a valid CAS Registry Number.